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A peculiarity of all-wheel drive off-highway vehicles is that their running abilities (cross-country mobility, tractive and velocity properties, turnability and the like) depend not only on total traction effort but also on its distribution between driving wheels. The latter is in great measure determined by actuating vehicle system and characteristics of the mechanisms installed in power dividing transmission units, i.e. in interwheel, interaxle reduction gears, and transfer cases. The characteristics of locking performance of these mechanisms regulate the circumferential force distribution between driving wheels and, respectively, a vehicle's performance indicators. Such mechanisms have been created and are being created in a multitude. The classification of power dividing mechanisms and system is given. They provide a high level of the traction performance of all-wheel drive off-highway vehicles and agricultural tractors, in particular.

Running abilities of an off-road, all-wheel drive vehicle depend considerably not only on total traction effort but also on its distribution among the drive wheels. This distribution is largely determined by mechanisms and systems installed in power dividing transmission units. These are interwheel differentials, interaxle reduction gears, and transfer cases. To control the wheel driving forces for obtaining the optimum vehicle properties, a more creative and efficient way to design wheel drive systems and to control vehicle running abilities is being proposed. Optimization criteria for the tractive and velocity properties, fuel consumption, turnability, and ride stability of a vehicle have been used for the mathematical optimization of the wheel driving forces. The vehicle is modeled in motion with taking into account the kinematic requirements.

Mass and geometric parameters of all-wheel drive off road vehicles, such as coordinates of the center of gravity and arrangement of the wheels, have been obtained to satisfy cross-country mobility profiles that reduce the dynamic normal loads on the running gear system. However, the influence of these parameters on tractive properties for basic cross-country mobility of vehicles receives less attention. The authors have developed a new method for determining mass and geometric parameters that provides optimal tractive properties for basic cross-country mobility of off-road vehicles. The methodology is realized using a mathematical model of a 6WD tractor on a deformable road surface. The mass and geometric parameters are achieved by optimizing the tractive efficiency function to provide the best transport efficiency on all running gears.